Of course the stereotype is that it’s because of the beer and whiskey. But as anyone who’s read Angela’s Ashes knows, long-term imbibing of alcohol does not always equal good times.

One thing I can say is that Irish people drink more tea per capita than anywhere else, including the English. And their tea is generally stronger. The traditional Irish way is the mix it with milk, so it’s got to be strong enough to hold up, and Irish Breakfast Tea therefore generally is darker (and has more caffeine) than most other kinds. Irish tea brands like Lyons and Barry’s have a lot of Assam in them, often mixed with Ceylon. According to an article on oldfashionedliving.com:

Irish tea is blended to be mixed with a lot of rich milk-up to 1/3 of the cup for some. The custom is to add the milk to the tea cup first, then pour in the tea. Irish breakfast tea is often a strong blend of Assam and Ceylon and most people would only drink it for breakfast….

Personally I’m not a fan of tea with milk or sugar, even though I like coffee with milk. Tea is just too watery. But if you’re looking for reasons why the Irish are known for being up for anything, being jacked up on sugar and caffeine is probably as good an answer as any.